In the manufacture of disposable absorbent articles, such as diapers, feminine care products, incontinence products, and the like, adhesives have typically been applied in a pattern of multiple, parallel glue lines which extend along the longitudinal dimension of the article. Such glue line patterns leave unbonded gaps between the lines, and the unbonded gap areas tend to have lower strength and lower integrity. As a result, the article can be more susceptible to stretching and tearing when adhesive tapes are employed to secure the article on the wearer, and the article may be less able to hold together and maintain its structure during use.
Sprayed and foamed adhesives have also been employed to assemble together various component layers of disposable absorbent articles. The adhesives may be thermoplastic-type adhesives or solvent-type adhesives. For example, see U.S. Pat. No. 3,523,536 to A. Ruffo and U.S. Pat. No. 4,118,531 to Minetola, et al. Swirled patterns of adhesive have been employed to construct articles such as shoes. For example, see U.S. Pat. No. 3,911,173 issued Oct. 7, 1975 to J. Sprague.
Various air forming techniques have been employed to form nonwoven fibrous webs. For example, U.S. Pat. No. 4,478,624 issued Oct. 23, 1984 to J. Battigelli, et al. describes a technique which employs a circular airflow component to help produce a more uniform distribution of fibers laid onto a foraminous conveyor. U.S. Pat. No. 2,903,387 issued Sept. 8, 1959 to W. Wade describes a technique for producing reticulated fibrous webs containing tubular or hollow fibers of elastomeric material. U.S. Pat. No. 2,950,752 issued Aug. 30, 1960 to P. Watson, et al. describes a spraying technique for forming relatively long, discontinuous, fine fibers of elastomeric materials. The fiber-forming liquid is extruded into and within a primary or high velocity stream of gas as a stream of plastic which is broken transversely into a plurality of fibers or fibrils before landing on a collector. U.S. Pat. No. 2,988,469 issued June 13, 1961 to P. Watson describes a further spraying technique for forming relatively long, discontinuous, fine fibers of non-elastomeric material. A high velocity jet stream of gas attenuate and fibrillates a single large-diameter plastic stream into a multiplicity of fibers and fibrils without the formation of shot.
Molded articles and preforms have been produced by depositing fibers into a form and binding the fibers together with a resin binder. For example, U.S. Pat. No. 3,796,617 issued Mar. 12, 1974 to A. Wiltshire describes a method for making a fibrous preform which comprises the steps of randomly depositing short reinforcing fibers on a form, binding the fibers together with a settable resin binder, and rolling the resin-coated fibers on the form into a dimensionally uniform porous mat. U.S. Pat. No. 3,833,698 describes a technique in which chopped fibers are directly deposited in a localized manner onto the interior surface of a screen form. The fibers are held in place by an airflow through the screen form into a vacuum chamber, and the deposited chopped fibers are sprayed with a heat-curable resin binder. U.S. Pat. No. 3,904,339 issued Sept. 9, 1975 to J. Dunn describes a technique for depositing glass fibers and curable resin into molds. A spray means for depositing the resin and fibers is supported on an arm which is pivoted about a selected axis.
Particular nozzle structures have been developed to form filaments from thermoplastic, melt-extrudable materials. The nozzles may be configured to produce a swirling air flow which disrupts the flow of extruded material into a plurality of fine fibers. For example, U.S. Pat. No. 4,185,981 describes a technique for producing fibers from a viscous melt. High-speed gas streams have a component in the tangential direction of the circular sectional surface of the melt, and a component which approaches the central axial line of the melt towards the flowing direction of the melt and then departs from the central axial line. The melt is continuously flown as fiber in the flowing direction and outwardly in the radial direction in a vortex form, which is spiral or helical or both. The fibrous melt which has flown away is accelerated and drawn into long fibers having a diameter of 10-100 microns, or short fibers having a diameter of 0.1-20 microns. The fibers can then be accumulated to form a fibrous mat.
U.S. Pat. No. 2,571,457 issued Oct. 16, 1951 to R. Ladisch describes a technique in which a cyclone of gas disrupts a "filament forming liquid" into fibers and/or filaments which may be collected on a moving belt. U.S. Pat. No. 3,017,664 issued Jan. 23, 1962 to R. Ladisch describes a fiber-forming nozzle wherein a fiber-forming liquid is spread over the outside wall of a circular body as a thin film, and wherein a stream of spiraling elastic fluid rotates at high velocity to draw out fibers which are picked up from the film of fiber-forming liquid.
U.S. Pat. No. 3,905,734 issued Sept. 16, 1975 to E. Blair describes an apparatus for continuously making a tube of meltblown microfibers. The meltblown microfibers are deposited longitudinally upon a circumferential surface of a mandrel and then are axially withdrawn from one end of the mandrel tube.
U.S. Pat. No. 3,543,332 issued Dec. 1, 1970 to W. Wagner, et al. describes a spinning nozzle for spray spinning molten fiber-forming materials and forming fibrous assemblies such as nonwoven fabrics and the like. The nozzle includes gas passages which are inclined so that their axes do not intersect the axis of an extrusion orifice in the nozzle. Gas streams act to swirl filaments formed from the fiber-forming material to produce a random expanding conical pattern as the filaments travel toward a moving collector.
An article entitled "Application Potential of Controlled Fiberization Spray Technology", Nonwovens Industry, January 1988, by J. Raterman describes a process for spraying pressure-sensitive hot-melts. The process employs a line of spray heads using nozzles with integral air jets that produce fine monofilaments of adhesive swirled at high speeds in a helix or spiral pattern.
Conventional spray techniques, such as those discussed above, have been excessively complex, and have not adequately regulated the distribution pattern and placements of the sprayed material onto a substrate. Ordinarily, the sprayed materials are deposited in a generally random pattern, and there can be excessive overspray and misplacement of the deposited materials. Where the sprayed materials are composed of adhesives, such as hot-melt adhesives, the overspray and misplacement can contaminate the equipment and require excessive maintenance. For the purpose of applying adhesives onto a substrate, the conventional techniques have not provided a sufficiently accurate control over the deposition pattern and have not been sufficiently flexible or readily adjustable to accommodate the placement of adhesives onto different widths of substrate. In addition, the conventional spray devices have been excessively sensitive to plugging when employed with viscous liquids, such as hot-melt adhesives.